HARQ process utilization in multiple carrier wireless communications

ABSTRACT

Methods and apparatus utilize hybrid automatic repeat request (HARQ) transmissions and retransmissions that are usable on multiple carriers, i.e. joint HARQ processes. For example, a downlink (DL) shared channel transmission of a joint HARQ process is received on one of the carriers. A first part of an identity of the joint HARQ process is determined by using HARQ process identity data received on a shared control channel. A second part of the joint HARQ process identity is determined using additional information. The joint HARQ process identity is then determined by combining the first part and the second part. A WTRU is provided that is configured to receive the DL shared channel and to make the aforementioned determinations. A variety of other methods and apparatus configurations are disclosed for utilizing joint HARQ processes, in particular in the context of DC-HSDPA.

This application is a continuation of U.S. patent application Ser. No.13/775,871, filed Feb. 25, 2013, now U.S. Pat. No. 8,700,968, issuedApr. 15, 2014, which is a continuation of U.S. patent application Ser.No. 13/567,746, filed Aug. 6, 2012, now U.S. Pat. No. 8,386,874, issuedFeb. 26, 2013, which is a continuation of U.S. patent application Ser.No. 12/429,011, filed Apr. 23, 2009, now U.S. Pat. No. 8,239,721, issuedAug. 7, 2012, which claims priority from U.S. Provisional Application61/048,149, filed Apr. 25, 2008, and U.S. Provisional Application61/086,973, filed Aug. 7, 2008, which are incorporated herein byreference as if fully set forth.

FIELD OF INVENTION

This application is related to wireless communication apparatus andmethods. In particular, methods and apparatus for wirelesscommunications that utilize hybrid automatic repeat request (HARQ)transmissions and retransmissions.

BACKGROUND

Evolved High-Speed Packet Access (HSPA) is a mobile data protocoldefined in the 3rd Generation Partnership Project (3GPP) release 7.Evolved HSPA includes increased data speed on the downlink (DL) from abase station (BS) and on the uplink (UL) to a BS, lower state transitionlatency, and longer battery life for mobile terminals. Evolved HSPA(HSPA Evolution) provides data rates up to 42 Mbit/s on the DL withmultiple input multiple output (MIMO) technologies and 11.52 Mbit/s onthe UL with higher order modulation.

The evolution of HSPA towards a higher throughput and lower latenciesrequires improvements to the physical layer, as well as thearchitecture. One improvement is the use of a Dual Cell-High SpeedDownlink Packet Access (DC-HSDPA) to increase the DL capacity and tosupport hot spot activities.

DC-HSDPA introduces a second DL carrier to be used as a second highspeed downlink packet access (HSDPA) channel. In DC-HSDPA, the dual celloperation applies to the high-speed downlink shared channel (HS-DSCH).In addition, the dual cells of DC-HSDPA are associated with a single BSand operate on different carriers. For example, one cell operates on ananchor carrier and the other cell operates on a supplementary carrierwhere both carriers are tranmitted by the same BS. Further, in Release 8of the HSPA specifications, the two cells of DC-HSDPA operate with asingle transmit antenna and the two cells operate over adjacent carriersin the same frequency band, although in future releases the same bandrestriction may be removed.

In such a dual-cell HSDPA network, BSs, referred to as Node-Bs in 3GPP,communicate to mobile terminals or other wireless transmit/receive units(WTRUs) over two distinct carriers simultaneously. This results indoubling the bandwidth, doubling the peak data rate available to WTRUs.It also has the potential to increase the network efficiency by means offast scheduling and fast channel feedback over two carriers.

As with conventional wireless apparatus, network stations and WTRUs forDual-Cell HSDPA communications are configured with multi-layercommunication processing components that implement a first physicallayer (L1) that transmits and receives the wireless signals, a mediumaccess control (MAC) layer (L2) and various higher layers.

In Dual-Cell communications, each WTRU is assigned a so-called anchorcarrier. The anchor carrier for the WTRU carries dedicated and shared DLcontrol channels, such as, for example, a fractional dedicated physicalchannel (F-DPCH), an enhanced dedicated channel (E-DCH) hybrid automaticrepeat-request (ARQ) indicator channel (E-HICH), an E-DCH relative grantchannel (E-RGCH), an E-DCH absolute grant channel (E-AGCH), a commonpilot channel (CPICH), etc. In addition anchor carrier for the WTRUcarries data channels, such as a HS-DSCH. The optional supplementary orsecondary carrier that serves the HS-DSCH cell carries data channels anda CPICH for the WTRU. The anchor carrier for a given WTRU may correspondto the supplementary carrier for another WTRU.

FIG. 1 shows an example evolved HSPA communications 100 using a DC-HSDPAsetup. Two DL carriers are shown, an anchor carrier A and asupplementary carrier B transmitted by a base station 101 to a WTRU 102over the same geographic area, along with a single UL carrier Atransmitted by the WTRU. The UL carrier A is associated with the anchorDL carrier A and also provides feedback associated with the secondsupplement DL carrier B.

Although only a single WTRU is illustrated, the DL carriers may beconcurrently utilized for wireless communications with other WTRUs. Asnoted above the supplementary DL carrier B for WTRU 102, may be beingused as an anchor carrier for another WTRU.

During low utilization periods of DC-HSDPA, it is possible that thesecond carrier may not be used, potentially underutilizing resources.This provides an opportunity to use the second carrier transmission as adiversity channel when it is not fully utilized for DL transmissions.

The typical number of HARQ processes used for wireless communication issixteen. With Dual-Cell HSDPA, there are two alternatives forassociating each carrier to hybrid ARQ (HARQ) entities: (1) Usingseparate HARQ entities, each HARQ entity is assigned to a given carrier(e.g., 8 HARQ processes per carrier) and (2) using joint HARQ entities,the HARQ entities are not linked to a specific carrier (e.g., all 16HARQ processes are available to both carriers). In the firstalternative, the HARQ retransmissions can only occur over the samecarrier. In the second alternative, the HARQ retransmissions can betransmitted over a different carrier, if desired.

FIG. 2 illustrates an example of a Universal Terrestrial Radio AccessNetwork (UTRAN) side MAC-enhanced high speed (MAC-ehs) architecture forDC-DSDPA with separate HARQ entities. FIG. 3 illustrate an example of aUTRAN side MAC-ehs architecture for DC-HSDPA with a joint HARQ entity.

Using separate HARQ entities has some implementation advantages. Byassigning each carrier to a HARQ entity, no change is required in Layer1 (L1) specifications and the current high speed shared control channel(HS-SCCH) type 1 can be used without modification. However, doing soreduces the fast scheduling gain, i.e. the gain obtained by exploitingthe fast channel variations independently over the two carrierfrequency, since retransmissions are then constrained to occur on thesame carrier as the initial transmission. Also, in cases where thesupplementary carrier is disabled, any on-going HARQ transmission on thesupplementary carrier would be blocked. This implies that either thecorresponding HARQ entities have to be flushed, resulting in loss ofdata and additional transmission delays, or that a new more complexprocedure needs to be devised to avoid losing data.

When using joint HARQ entities on the other hand, the scheduler can takefull advantage of the varying radio conditions and, in addition, allactive HARQ processes can be maintained when de-activating thesupplementary carrier. Therefore, there are significant advantages tousing joint HARQ entities.

While using joint HARQ entities is advantageous, it requires additionalsignaling. The existing HS-SCCH type 1 only carries three bits for HARQprocess information. This is insufficient to address the 16 HARQprocesses that are typically available with joint HARQ entities.

Under Long Term Evolution-Advanced (LTE-A) standards, carrieraggregation and support of flexible bandwidth arrangement may besupported. This allows DL and UL transmission bandwidths to exceed 20MHz. In Release 8 (R8) LTE, for example, a 40 MHz bandwidth isspecified. This improvement will also allow for more flexible usage ofthe available paired spectrum. For example, R8 LTE is limited to operatein symmetrical and paired FDD mode, e.g., DL and UL must have the sametransmission bandwidth, e.g., 10 MHz, 20 MHz, and so on. However, LTE-Ashould be able to support operation in asymmetric configurations such asa 10 MHz DL carrier paired with a 5 MHz UL carrier. In addition,composite aggregate transmission bandwidths should also possible withLTE-A, e.g., a first 20 MHz DL carrier and a second 10 MHz DL carrierpaired with a 20 MHz UL carrier and so on. Additionally, compositeaggregate transmission bandwidths may not necessarily be contiguous infrequency domain, e.g., the first 10 MHz so-called component carrier inthe above example could be spaced by 22.5 MHz in the DL band from thesecond 5 MHz DL component carrier. Alternatively, operation incontiguous aggregate transmission bandwidths should also be possible,e.g., a first 15 MHz DL component carrier is aggregated with another 15MHz DL component carrier and paired with a 20 MHz UL carrier.

In a LTE-A system, the physical downlink control channels (PDCCHs) orDownlink Control Information (DCI) messages contained therein carryingthe assignment information can be separately transmitted for thecomponent carriers containing the accompanying physical downlink sharedchannel (PDSCH) transmissions. For example, if there are two componentcarriers, there are two separate DCI messages on each component carriercorresponding to the PDSCH transmissions on each component carrierrespectively. This is referred as separate PDCCH coding.

Alternatively, the two separate DCI messages for a WTRU may be sent onone component carrier, even though they may pertain to accompanyingdata, or PDSCH transmissions on different component carriers. Theseparate DCI messages of PDCCHs for a WTRU or a group of WTRUs can betransmitted in one or in multiple carriers, and not necessarily all ofthem on every component carrier. This is referred to as an anchorcarrier with separate PDCCH coding.

The DCI carrying the assignment information for PDSCH(s) on more thanone component carrier can be encoded jointly and carried by one singlejoint DCI control message, or PDCCH message. This is referred to asjoint PDCCH coding. One approach for the dynamic support of multicarrierassignment schedules is to have a variable size DCI format with a commonDCI part and a carrier specific part. The common DCI part contains afield indicating which component carrier is being assigned in thecurrent subframe and implicitly which carrier specific DCI format willfollow. The common DCI format may also contains information that couldapply to all carriers such as Hybrid ARQ process.

Accordingly, a method and apparatus configured to provide the necessarymechanisms to signal the HARQ process information in a DC-HSDPA systemor LTE-A system with joint HARQ entities and to effectively utilize theunused resources in supplementary component carriers to expand systemperformance and reliability is desired.

SUMMARY

Methods and apparatus are provided for utilizing hybrid automatic repeatrequest (HARQ) transmissions and retransmissions that are usable onmultiple carriers, i.e. joint HARQ processes, for a wirelesscommunication of data. In one embodiment of a method, a downlink (DL)shared channel transmission of a joint HARQ process is received on oneof carriers. A first part of an identity of the joint HARQ process isdetermined by using HARQ process identity data received on a sharedcontrol channel. A second part of the joint HARQ process identity isdetermined using additional information. The joint HARQ process identityis then determined by combining the first part and the second part.

A WTRU is provided that is configured to receive the DL shared channeland to make the aforementioned determinations. A variety of othermethods and apparatus configurations are disclosed for utilizing jointHARQ processes, in particular in the context of DC-HSDPA.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawings.

FIG. 1 is a diagram of a Dual-Cell High-Speed Downlink Packet Access(DC-HSDPA) wireless communication.

FIG. 2 is a diagram of an example of a UTRAN side MAC-ehs architecturefor DC-HSDPA with separate HARQ entities;

FIG. 3 is a diagram of an example of a UTRAN side MAC-ehs architecturefor DC-HSDPA with a joint HARQ entity.

FIG. 4 is a diagram of an example wireless communication systemincluding a plurality of wireless transmit/receive units (WTRUs), a basestation, and a radio network controller (RNC);

FIG. 5 is a functional block diagram of a WTRU and the base station ofFIG. 4.

FIG. 6 is a diagram of an example of joint coding of data across twocarrier channels.

FIG. 7 is a diagram of an example of an embodiment usingnon-simultaneous carrier-independent HARQ processtransmissions/retransmissions.

FIG. 8 is a diagram of an alternate example of an embodiment usingpossibly simultaneous carrier-independent HARQ processtransmissions/retransmissions.

FIG. 9 is a diagram of an example of encoding using a new HS-SCCH typeDC to support full signaling of 16 HARQ processes.

DETAILED DESCRIPTION

When referred to hereafter, the terminology “wireless transmit/receiveunit (WTRU)” includes but is not limited to a user equipment (UE), amobile station, a fixed or mobile subscriber unit, a pager, a cellulartelephone, a personal digital assistant (PDA), a computer, or any othertype of user device capable of operating in a wireless environment. AWTRU may be configured to operate in one or more warless systemsincluding, but not limited to, a Long Term Evolution (LTE) environmentor a Universal Mobile Telecommunications System (UMTS). When referred tohereafter, the terminology “base station” includes but is not limited toa Node-B, evolved universal terrestrial radio access (E-UTRA) Node-B(eNB), a site controller, an access point (AP), or any other type ofinterfacing device or network station capable of operating in a wirelessenvironment. When referred to hereafter, the term “carrier” refers to acarrier frequency. Although many examples refer to combining twocarriers, there is no inherent limitation on the number of carriers.

FIG. 4 shows a wireless communication system 400 including a pluralityof WTRUs 410, a base station 420, and a radio network controller (RNC)430 that may control multiple base stations. As shown in FIG. 4, theWTRUs 410 are in communication with the base station 420, which is incommunication with the RNC 430.

Although three WTRUs 410, one base station 420, and one RNC 430 areshown in FIG. 4, any combination of wireless and wired devices may beincluded in the wireless communication system 400. Although the RNC 430is shown in the wireless communication system 400, the RNC 430 may notbe included in some wireless systems such as LTE, where the base station420 may be configured as an Evolved UTRAN Node-B (eNB).

FIG. 5 is a functional block diagram 500 of a WTRU 410 and the basestation 420 of the wireless communication system 400 of FIG. 4. As shownin FIG. 5, the WTRU 410 is in communication with the base station 420and both may be configured to perform the methods of data reception in awireless communication network disclosed below.

In addition to the components that may be found in a typical WTRU, suchas a display (not shown), the example WTRU 410 includes a processor 515,a receiver 516, a transmitter 517, and an antenna 518. The processor 515is configured to facilitate the implementation of the methods ofimproving data reception disclosed below. The receiver 516 and thetransmitter 517 are in communication with the processor 515. The antenna518 is in communication with both the receiver 516 and the transmitter517 to facilitate the transmission and reception of wireless data.

In addition to the components that may be found in a typical basestation, such as a display (not shown), the base station 420 includes aprocessor 525, a receiver 526, a transmitter 527, and an antenna 528.The processor 525 is configured to facilitate the implementation of themethods of improving data reception disclosed below. The receiver 526and the transmitter 527 are in communication with the processor 525. Theantenna 528 is in communication with both the receiver 526 and thetransmitter 527 to facilitate the transmission and reception of wirelessdata.

The WTRU configuration is typically set up to complement the type ofsignaling that is received from the base station. For example, the WTRUconfiguration may be implemented by the WTRU receiving a configurationmessage from the base station which message may originate with the RNC.Accordingly, a WTRU can be configurable into a variety of configurationsso the WTRU can operate to receive the two carriers 541, 542 fordifferent BS transmission environments.

In an example of a first BS transmission environment, the BS 420 isconfigured to transmit identical data on a first anchor carrier 541 andon a second supplementary carrier 542 to thereby exploit frequencydiversity. Once the identical data is received by the WTRU it may thenbe processed in various manners.

In a first example configuration for implementing such processing, theWTRU's receiver 516 receives the two carriers 541, 542 via antenna 518that carry the same information. The processor 515 in conjunction withthe receiver 516 then combine the two carriers 541, 542 at baseband anddecode the combined signal. The processor 515 decodes the added signalas if only one signal has been received at the WTRU. This examplerequires minimal complexity because the WTRU is only required to add twobaseband signals, and a single receiver chain may be used to recover thereceived data.

In a second example configuration for implementing such processing, theWTRU may be configured to combine the two carriers 541, 542 that carrythe same information based on the signal strength of each carrier. TheWTRU can be configured to assign a higher weight to the carrier with thehigher signal-to-noise ratio (SNR). After the WTRU assigns a weight toeach carrier 541, 542, the WTRU combines the two carriers at basebandinto a single receiver chain. The WTRU then decodes the combined signal.The SNR can be based, for example, on measurements from a common pilotchannel (CPICH) or a high-speed shared control channel (HS-SCCH).

In a third example configuration for implementing such processing, theWTRU can be configured to demodulate each of the received carriers 541,542 and then to combine the two carriers at a soft bit level. After thecarriers 541, 542 are combined, the WTRU then decodes the combinedsignal. In this example, two demodulator chains and soft-bit combiningare required before the WTRU decodes the combined signal.

In a fourth example configuration for implementing such processing, theWTRU can be configured to use two full receiver chains rather than asingle receiver chain. In this option, the WTRU processes each carrierseparately and then selects the carrier data that passes a cyclicredundancy check (CRC). This example configuration adds a full secondchain and does not provide any combining gain. Moreover, this exampleconfiguration is more complex because it adds more hardware to process asecond full receiver chain.

According to another BS transmission environment, the BS 420 isconfigured to able to transmit different coded data from the same datablock. Accordingly, the coded data on the first carrier 541 may bedifferent from the coded data on the second carrier 542. In thisenvironment, once the different coded data is received by the WTRU 410,the WTRU 410 is configured to process each carrier 541, 542 separatelyand the WTRU 410 can be configured to select carrier data that passes aCRC. The BS 420 may code the data in each carrier 541,542 a variety ofways.

The coding for each carrier 541, 542 can be based on channelcharacteristics or the coding for each carrier can be pre-defined.Further, the modulation and coding in the first carrier 541 and thesecond carrier 542 may be optimized for different fading channels toensure that at least one of the carriers 541, 542 is likely to alwaysperform well.

Alternatively, the BS 420 may code the user data differently for eachcarrier 541, 542, but in such a manner that the WTRU 410 may combine aplurality of coded data packets at the soft symbol or the soft bit levelbefore attempting to decode the packets. The BS 420, accordingly, mayuse different redundancy versions (RVs) and/or different code rates anddifferent radio resources for retransmissions. Effectively, the BS 420sends two transmissions, which would otherwise be a “first transmission”and a “second transmission” of the same hybrid automatic repeat-request(HARQ) process, simultaneously rather than sequentially. Additionally,different code rates, modulation types, and powers may be used ondifferent carriers for additional link adaptation or schedulerflexibility.

In addition, the BS 420 may operate without the HS-SCCH when the twotransmissions are sent simultaneously across the two carriers 541, 542.In this case, the WTRU 410 can be configured to simultaneously monitorpairs of high speed physical downlink shared channels (HS-PDSCH) (one ortwo HS-PDSCH per carrier). The first transmission, over the two carriers51, 542, is sent without any associated HS-SCCH(s), whereas theretransmission is performed with the associated HS-SCCH(s). The RV ofthe HS-PDSCH transmitted over the anchor and supplementary carriers maybe pre-defined or alternatively, configured by the network for alltransmissions.

At each transmission time interval (TTI) when transmission to the WTRUis possible, the WTRU 410 can be configured to attempt to decode from aset of configured HS-PDSCH codes, a potential data block transmittedover the two HSDPA carriers. Where a discontinuous reception (DRX)configuration is used by the WTRU, DRX parameters will typically controlwhen transmission to the WTRU is possible.

For such decoding, the WTRU 410 can be configured to de-spread thereceived signals after demodulation according to the specific HS-PDSCHchannelization codes of interest and to store the resulting symbols fromboth the anchor and supplementary carriers in an incremental redundancybuffer according to the pre-configured or configured RV associated witheach carrier. The WTRU 410 is configured to then attempt to decode thebuffer contents. If a CRC is successful, then the data is passed on tohigher layers. Otherwise, the WTRU 410 attempts to decode from a new setof channelization codes. Once all of the configured HS-PDSCH codes areexhausted, the procedure is completed for the current TTI. At a nextTTI, the same operations can be performed again. This allows a reductionof latencies associated with HARQ round-trip time (RTT) for real-timeservice applications such as Voice over Internet Protocol (VoIP).

Alternatively, the BS 420 may avoid the transmission of the HS-SCCH overtwo carriers 541, 542, where re-transmission, after the initialsimultaneous transmission of the two RVs over the two carriers 541, 542,is not possible. In such BS transmission environment, the WTRU 410 canbe configured to not monitor the HS-SCCH, and to not transmit anacknowledged/not acknowledged (ACK/NACK) indication (feedback) becausethe BS will not retransmit. However, the WTRU 410 may benefit fromdiversity between the two RVs. The WTRU 410 can be configured to attemptto decode the HS-PDSCH channels of both carriers 541, 542 during theTTIs where it is possible that data is transmitted for the WTRU 410consistent with DRX parameters, if configured.

In another alternative, the BS may reduce transmission of the HS-SCCH,by being configured to transmit the RVs simultaneously over bothcarriers 541, 542 during retransmission. The initial transmission, whichis without the HS-SCCH, is performed on either the anchor carrier 541 orthe supplemental carrier 542.

The following describes the case where both carriers 541, 542 transmitthe same medium access control (MAC) level data, but using differentmodulation, RV and/or code rate. In this case, the BS 420 transmits thescheduling information of both carriers over one HS-SCCH on the anchorcarrier, or alternatively, on the supplementary carrier. Additionally, anew type of HS-SCCH may be defined that is used when the network sendsthe same user data over both carriers 541, 542.

In one option, both carriers 541, 542 use the same modulation and samechannelization codes on both resources; however, the RV used for thephysical data over both carriers 541, 542 is different. A pre-definedmapping may be used in the network and the WTRU 410 between the RV usedin the anchor and supplementary carriers. This allows the BS 420 tosignal the scheduling of both carriers 541, 542 over one HS-SCCH and useonly one field for the RV and HARQ process. Upon the reception of theHS-SCCH, the WTRU 410 uses the signaled RV to decode the data on theanchor carrier. In such case, the WTRU 410 can be configured to use thepre-defined mapping to generate or find an index to the RV of thesupplementary carrier. For example, the following formula can be used todetermine the index to the three bit index to the RV coding for thesupplementary carrier:Xrvsup=(Xrv+n) mod 8  Equation (1)where Xrv is a three bit index signaled over the HS-SCCH to the WTRU410, indicating the index to the RV coding for the anchor carrier, and nis a parameter that is configured by the network or by the WTRU 410 andn may have a value of 0 or any positive integer.

Additionally, the modulation used can be different for both carriers541, 542, wherein the BS 420 may use two fields in the HS-SCCH, which istransmitted over the anchor or the supplementary carrier, to indicatethe modulation and only one field is used for the RV.

In another BS transmission environment, the BS 420 is configured to usejoint coding of the data across the two carrier channels. Referring toFIG. 6, the BS 420 encodes the data into a single coded block 620, whichmay be performed with code block segmentation. Then the BS 420 dividesthe coded block 620 into two coded segments. The coded block 620 may beprocessed as a single block using only one CRC 615 (as shown) for theentire block, or alternatively there may be one CRC per code segment(i.e., one CRC per carrier), or one CRC per code block segment. Onecoded segment 630 will be sent over a first carrier and a second codedsegment 640 will be transmitted over a second carrier. The codedsegments (630 and 640) are sent over their respective DL carriers to aWTRU 410. The WTRU 410 receives and demodulates and jointly decodes thesignals. The basic coding methods implemented in the 3GPP standard areapplicable, while other variations may be applicable as well. Forexample, a lower rate turbo code may be used as the basic code prior topuncturing. A low-density parity-check (LDPC) code may also be applied.The coded data is segmented between the first carrier 541 and the secondcarrier 542 without any fundamental impact on the interleaving and ratematching functions in each carrier. Different effective per-carrier coderates may be used on the different carriers 541, 542, for example, thecode rate for the part of the coded segment transmitted on the firstcarrier 541 may be different than the rate on the second carrier 542. Inaddition, different modulation types and powers may also be used on thedifferent carriers 541, 542 for dynamic link adaptation, capacity, orscheduler flexibility. Alternatively, space-time block coding basedtransmit diversity (STTD) codes may be used for transmit diversity intwo antennas. Similarly, STTD processing may be used at the WTRU.

In another BS transmission environment, the BS 420 is configured to useintelligent scheduling and retransmission of data. The BS 420 isconfigured to compare performance, e.g. performance measurements and/orperformance statistics, between the two carriers based on a channelquality indicator (CQI) feedback or CQI report for previouslytransmitted timeslots. The carrier with better performance may be biasedfor higher load to maximize data throughput. Adaptive Modulation andCoding (AMC) may be used in conjunction to produce maximum capacity andutilization. Further, for a group of WTRUs, each may be assigned to usethe different dual carriers to provide improved load balancing, eithersemi-statically or dynamically, based on WTRU/carrier channel qualities.

FIG. 7 shows an example of a BS transmission in an environment usingnon-simultaneous carrier-independent HARQ processtransmissions/retransmissions. In this example, a single transportblock, such as a MAC layer protocol data unit (PDU) containing userdata, is transmitted by a single HARQ process. The HARQtransmissions/retransmissions are independent from the DL carriers 541,542.

The BS 420 may transmit a first downlink HARQ transmission on a firstcarrier and may transmit one or more HARQ retransmissions on a differentcarrier. In the example of FIG. 7, the BS 420, using a HARQ process 1(HARQ #1), transmits a HARQ #1 transmission (Tx) 705 on DL Carrier A702. The BS receives a NACK 714 over the UL from the WTRU that,accordingly, requires a retransmission. The HARQ #1 process sends HARQ#1 retransmission (RTx) 708 on Carrier B 703. Another NACK 716 isgenerated by the WTRU and received by the BS that, accordingly, requiresanother retransmission. The BS using HARQ #1 process again retransmitsby sending HARQ #1 retransmission 710 on Carrier B 403. A further NACK718 is generated by the WTRU and received by the BS that, accordingly,requires a further retransmission. The BS using HARQ #1 process thensends a further HARQ #1 retransmission 712 on Carrier A 702.

In addition to generating NACKs, the WTRU may also generate and send onthe UL to the BS CQI reports. The decision to switch carriers for theretransmissions as illustrated in the example of FIG. 7 may be madebased on a CQI report 704. For example, channel quality may be comparedto a channel quality threshold value and/or traffic may be compared to atraffic load threshold value. This provides more flexibility to the BS,such that the BS can attempt to optimize the scheduling of usertransmissions and retransmissions based on channel quality and/ortraffic load that is reported on each carrier.

FIG. 8 shows an example of a BS transmission in environment thatprovides for the possible use of simultaneous carrier-independent HARQprocess transmissions/retransmissions. In this example, two MAC PDUs aretransmitted by the BS using two HARQ processes. HARQ process #1 and HARQprocess #2 concurrently commence transmissions 805 and 807,respectively, on Carrier A 802 and Carrier B 803. For both HARQprocesses, the WTRU generates NACKs 818 requiring both processes toretransmit. A first retransmission for each HARQ process, HARQ #1retransmission 808 and HARQ #2 retransmission 810, is transmitted onCarrier B 803. In the example, these retransmissions fail so thatrespective NACK 820 and NACK 824 are generated by the WTRU which is alsogenerating and reporting CQI reports 804 to the BS on the UL.

The BS may decide to change the carrier for the HARQ processretransmission if the CQI reported for one carrier is significantlybetter than the CQI report for the other carrier, e.g. channel qualitymay be compared to a channel quality threshold value and/or traffic maybe compared to a traffic load threshold value. In the example of FIG. 8,after the failure of both first retransmissions, a BS decision isreflected whereby HARQ #1 continues to retransmit 812 on Carrier B 803and HARQ #2 retransmits on Carrier A 802. The example reflects that thesecond HARQ #2 retransmission succeeds, indicated by the WTRU generatingan ACK 828. The second HARQ #1 retransmission 812 fails as indicated byNACK 826. The BS makes a decision to change carriers for HARQ #1 processbased upon a CQI report 804 and send further HARQ #1 retransmission 816on Carrier A 802.

In order to allow the carrier-independent HARQ processes, the scope ofthe HARQ process number that is sent to the WTRU should be valid acrossboth carriers. Carrier-independent HARQ processes and joint HARQprocesses between carriers may be used interchangeably. Joint HARQprocesses between N carriers and carrier-independent HARQ processesrefer to a set of HARQ processes for which transmissions andretransmissions may be carried over any of the N carriers. A joint HARQprocess can be defined as one HARQ process belonging to a set of jointHARQ processes.

The following approaches for addressing HARQ processes utilizingcarrier-independent HARQ retransmission have little or no impact to L1signaling. These approaches do not require any L1 protocol re-design. AWTRU is preferably configured to determine the identity of a joint HARQprocess from such addressing. The WTRU then may use that determinedidentity to process the data transmissions and retransmissions of theidentified HARQ process.

Four bits are needed to independently address, i.e. identify, 16 HARQprocesses. For one embodiment, three existing HARQ process informationbits, X_(hap,1), X_(hap,2), X_(hap,3) that are carried on the HS-SCCHtype 1 to indicate a first part of a HARQ process identity are used incombination with additional information. The additional information mayinclude a HS-DSCH radio network temporary identifier (H-RNTI), timinginformation, a new data (ND) indicator bit (NDI), or the channelizationcode of the HS-SCCH to provide the necessary 4th bit for the second partof the HARQ process identity denoted by X_(hap,4). Thus, the full 16HARQ processes can be addressed, i.e. identified, by using X_(hap,1)through X_(hap,4). Thus, the combination of X_(hap,1) through X_(hap,4),i.e. the first part of the HARQ process identity combined with thesecond part of the HARQ process identity, yields the full HARQ processidentity. X_(hap,4) may be an information field or element of one ormore bits depending on the number of HARQ processes that are jointlyused.

X_(hap,4) is not constrained to be in any specific position with respectto the other bits, X_(hap,1), X_(hap,2), X_(hap,3), addressing the HARQprocesses, e.g. X_(hap,4) is not necessarily the least significant bitor the most significant bit. Where multiple HARQ entities exist, e.g.two HARQ entities, X_(hap,4) can be interpreted as indicating to whichHARQ entity the HARQ process under consideration belongs. In otherwords, X_(hap,4) can be considered as an “additional information,” thatmay be used to uniquely identify or address a subset or group of HARQprocesses, which are then further addressed by the 3 existing HARQprocess information bits carried on the HS-SCCH. For instance, in thecase where 16 HARQ processes are jointly used between two carriers, theadditional information or X_(hap,4) may indicate whether thetransmission belongs to a first set of 8 HARQ processes or a second setof 8 HARQ processes. Once the group is determined by this additionalinformation, X_(hap,1), X_(hap,2), and X_(hap,3) can be used todetermine the HARQ processes within the group.

In one example, a second or a plurality of H-RNTI may be provided to theWTRU by the network using radio resource control (RRC) signaling, forexample, via a configuration message. The WTRU can then be configured tomonitor for all such provided H-RNTIs simultaneously. The WTRU canaccordingly be configured to decode an associated HS-PDSCH and identifya HARQ process when the WTRU receives an HS-SCCH carrying one of theassigned H-RNTIs. The HARQ process identity can then be derived forexample by setting X_(hap,4) to “0” (or alternatively “1”) if theprimary H-RNTI is used and “1” (or alternatively “0”) if the secondaryH-RNTI is used. If multiple H-RNTIs are used, the value of X_(hap,4) orthe group which the H-RNTIs are addressing can be explicitly signaled bythe RRC or alternatively it can be implicitly determined based on theorder of the configured H-RNTIs. The first H-RNTI may correspond thefirst group, the second to the second group, etc.

This example allows the reuse of existing coding formats of the HS-SCCH.This may be problematic when many WTRUs are present in a cell, since thenumber of usable H-RNTI is typically limited.

Where the supplementary carrier is deactivated, the WTRU may beconfigured to continue to monitor all provided H-RNTIs and make use ofall 16 HARQ processes. Alternatively, the WTRU may be configured to stopmonitoring the secondary H-RNTI or the primary H-RNTI. In the lattercase, upon deactivation of the carrier, the WTRU may be configured toflush the buffer of the HARQ processes and only use one HARQ entity.

In another embodiment, the WTRU may be configured, for example, byreceiving a configuration message from the network, to facilitateprocessing of joint HARQ processes or independent HARQ processes, i.e.,HARQ processes associated with a specific carrier. More specifically, asecond H-RNTI may be used as an optional parameter that, if present,implies that the 16 HARQ processes can be used by any of the twocarriers. Otherwise, if only one H-RNTI is provided to the WTRU, theabsence of the second H-RNTI may be used to imply that each HARQ entityis associated with a specific carrier.

In such embodiment, the WTRU may be configured to re-interpret one bitin the existing HS-SCCH to signal the value of X_(hap,4). For example,the NDI bit (X_(nd,1)) may be re-interpreted when DC-HSDPA operationsare enabled to indicate the value of X_(hap,4). The NDI bit can act asthe additional information that signals whether the HARQ process belongsto the first group or the second group.

This embodiment has the advantage of allowing the reuse of existingcoding formats of the HS-SCCH, since it makes use of the same totalnumber of information bits as these formats, but may restrict thescheduler. If the WTRU is configured to re-interpret X_(nd,1), thisimplies that the scheduler is limited to using incremental redundancy inDC-HSDPA, as opposed to being able to also use chase combining. However,this particular limitation is not extremely important since suchlimitation is also imposed for multiple input multiple output (MIMO)mode operations.

In this embodiment, the timing of the HS-SCCH transmission, orequivalently, the timing of the associated HS-PDSCH transmission may beused to indicate the value of X_(hap,4). The timing is best defined atthe subframe level (2 ms). For example, “even” values of HS-SCCHsubframe numbers may correspond to X_(hap,4)=0, while “odd” values ofHS-SCCH subframe numbers may correspond to X_(hap,4)=1, or vice versa.Since there is an odd number of HS-SCCH subframes within a frame andsince the subframe numbers cycle every frame, this approach results inX_(hap,4) values corresponding to the even HS-SCCH subframes that areused more often than X_(hap,4) values corresponding to the odd HS-SCCHsubframes. Thus, the NodeB scheduler will provide more opportunities touse certain subsets of HARQ processes over other subsets of HARQprocesses.

To avoid the limitation of having more opportunities to signal certainHARQ processes more than others, the value of X_(hap,4) may additionallybe based on a frame counter. For example, in addition to the HS-SCCHsubframe number, the connection frame number (CFN) may be used suchthat, for example, over two frames, the number of times X_(hap,4)=0 isthe same as X_(hap,4)=1. One way to achieve this is by using thefollowing formulation for setting the value of X_(hap,4):X _(hap,4)=(5×CFN_HSSCCH+S_HSSCCH) mod 2,  Equation (2)where CFN_HSSCCH and S_HSSCCH are respectively, the connection framenumber and the subframe number of the HS-SCCH transmission. Differenttimers and counters may be used to achieve similar results.

With this approach, each HARQ process is available for transmission in agiven carrier every other subframe, and a transmission from a HARQprocess is possible every sub-frame on one of the two carriers. Thus,the NodeB scheduler benefits from the possibility of transmitting orre-transmitting on the best carrier within a window of two sub-framesthereby providing carrier-diversity. Since in many scenarios the channelcorrelation between two successive sub-frames is higher than between thetwo carriers, this approach yields better performance than usingseparate HARQ entities. However, there is a cost of a possibleadditional transmission delay of one sub-frame.

One potential issue with the timing-based HARQ process indication is thescenario where one of the carriers, for example the supplementarycarrier, is being de-activated. The BS and WTRUs can be configured toimplement one or more of several options to handle this situation.

In an example of a first option, upon de-activation of the supplementarycarrier or after a pre-defined duration after the de-activation, half ofthe HARQ processes are de-activated and the corresponding HARQ entitiesare flushed. The remaining HARQ processes are available to everysub-frame in the remaining anchor carrier. This approach may result inloss of data unless the HARQ processes are prevented from being disabledfor a certain period prior to de-activation.

In an example of a second option, all 16 HARQ processes are maintainedwhen the supplementary carrier is disabled and the timing-based HARQprocess indication is maintained. This means that a given HARQ processis available every other subframe in the remaining anchor carrier. Thisapproach has the advantage of avoiding any loss of data uponde-activation while still allowing the WTRU to transmit continuously. Asmall drawback is that the timing of the retransmissions for a certainHARQ process cannot be chosen within an interval of two sub-frames.

In an example of another embodiment, a WTRU is configured to use thechannelization code to determine the value of the X_(hap,4). Morespecifically, the WTRU may be configured, for example by receiving aconfiguration message, with two sets of channelization codes in eachcarrier which can be used to determine X_(hap,4). For instance, the oneset of channelization codes may signal “0” and the other setchannelization codes may signal “1”.

Alternatively, the network may signal the HS-SCCH channelization codeset, and the WTRU and network are pre-configured to use the first halfHS-SCCH codes of the signaled set from the RRC to signal “0” and thesecond half of the set to signal “1”. Alternatively, the codes arenumbered from 0 to 3 in the order of the signaled set in the RRC messagethen the WTRU and network can be pre-configured to use the odd numberedcodes to signal “0” and the even numbered codes to signal “1” or viceversa.

In such an embodiment, a new HS-SCCH type may be introduced to supportfull signaling of the 16 HARQ processes. When DC-HSDPA is enabled, thenetwork may use this new HS-SCCH type, “HS-SCCH type DC.” HS-SCCH typeDC may contain an additional bit, over and above the conventionalHS-SCCH type, that enables the signaling of 16 HARQ processes. This maybe accomplished, for example, by deriving the HS-SCCH type DC from theHS-SCCH type 1, with an additional bit in the HARQ process informationfield. Thus, the new HS-SCCH type DC may carry the followinginformation, where changes with respect to HS-SCCH type 1 areunderlined:

-   -   Channelization-code-set information (7 bits): x_(ccs,1),        x_(ccs,2), . . . , x_(ccs,7)    -   Modulation scheme information (1 bit): x_(ms,1)    -   Transport-block size information (6 bits): x_(tbs,1), x_(tbs,2),        . . . , x_(tbs,6)    -   Hybrid-ARQ process information (4 bits): x_(hap,1), x_(hap,2),        x_(hap,3), x_(hap,4)    -   Redundancy and constellation version (3 bits): x_(rv,1),        x_(rv,2), x_(rv,3)    -   New data indicator (1 bit): x_(nd,1)    -   WTRU identity (16 bits): x_(ue,1), x_(ue,2), . . . , x_(ue,16)

As shown in FIG. 9, the encoding for the new HS-SCCH type DC may alsofollow the existing encoding for HS-SCCH type 1, with the distinctionthat an additional HARQ process information bit or bit field is present.That is, all the elements have their conventional meaning, except forthose directly affected by the addition of a bit field for X′_(hap). X′₂is altered since it is generated by multiplexor 940 using X′_(hap),X_(tbs), and X_(nd). The WRTU specific CRC attachment processing block950, channel coding processing block 960, and rate matching 2 processingblock 970 are modified to accommodate the additional information and thedimensions of Y′₂, and Z′₂ are accordingly altered.

X′_(hap), in this example, may consist of the 4 bits X_(hap,1),X_(hap,2), X_(hap,3), X_(hap,4). As a consequence, X′₂ has an additionalbit and may consists of a sequence of bits x′_(2,1), x′_(2,2), . . . ,x_(2,13) wherex′_(2,i)=x_(tbs,i) i=1,2, . . . ,6x′_(2,i)=x_(hap,i-6) i=7,8,9,10x′_(2,i)=x_(rv,i-9) i=12,13,14x′_(2,i)=x_(nd,i-12 i=)14The WRTU specific CRC attachment 950 can be calculated using thesequences X₁ and X′₂ in the same way it is calculated for the HS-SCCHtype 1 using X₁ and X₂, and the WTRU-specific identity X_(ue),specifically, the 16-bits H-RNTI. This leads to Y′₂ with one additionalbit, and Z′₂ with 3 additional bits.

To compensate for the additional bits, the “Rate matching 1” procedure972 from the HS-SCCH type 1, is modified. In particular, the sequence ofbits Y′₂ for HS-SCCH type DC carries 30 bits, as opposed to 29 bits forYin HS-SCCH type 1. This results in modifying the “Rate matching 2”procedure 970, from the conventional puncturing of 31 bits for HS-SCCHtype 1, to the puncturing of 34 bits, i.e. the puncturing of 3 extrabits. The resulting change in coding rate is almost insignificant:0.3750 for HS-SCCH type DC versus 0.3625 for HS-SCCH type 1. The smalldifference can be compensated for by using slightly more power totransmit the HS-SCCH DC, if necessary.

The resulting sequence R′₂, which corresponds to the second part of theHS-SCCH is finally physical channel mapped with the first part of theHS-SCCH, namely, sequence S₁. This results in the full HS-SCCH.

Sequence S₁ can be obtained the same way as in the conventionalprocedure. The channelization code-set bits X_(ccs) are firstmultiplexed 942 with the modulation scheme bit X_(ms) to form sequenceX₁. The sequence X₁, conventionally 8 bits, is then channel-coded 962using a convolution code resulting in the sequence Z₁, conventionally 48bits. Z₁ is then punctured to give a conventional 40 bits output R₁.Next WTRU specific masking 982 is performed. A WTRU-specific maskingsequence of 40 bits is exclusively ORed (XORed) with R₁, the maskingsequence being a function of the WTRU identity X_(ue), specifically the16-bit H-RNTI. The WTRU specific masking 982 results in a new 40 bitsequence, S₁.

While the BS transmission environments described above are described interms of two carriers using joint HARQ processes, the methods describedherein are applicable to multi-carrier operations where a WTRU isconfigured to operate with more than one carrier, for example, byreceiving a configuration message. In the case of multi-carrieroperation or when more than 16 HARQ processes are shared, the networkmay use more than two H-RNTI, or more than two channelization codes toidentify the group of HARQ processes, or more than 2 timingconfigurations, etc.

Alternatively, in another environment, particular carriers may be pairedwith another carrier and jointly use the HARQ processes. For instance,if 4 carriers are configured, two pairs of two carriers will beconfigured and allowed to use joint HARQ processes. The addressing ofthe HARQ processes within the paired carriers may be performed using oneof the embodiments described above, such as the H-RNTI, timing,channelization code, introduction of a new HS-SCCH type, NDI, etc. AWTRU with carrier aggregation or multi-carrier configured by higherlayers with component carriers 1, 2, . . . N, and with separate PDCCHcoding, can take advantage of a joint HARQ entity shared among allconfigured component carriers, so that retransmission can occur on anyof the N component carriers where N is any positive integer. The jointHARQ entity may be composed of N times 8 processes, since there aretypically 8 processes per HARQ entity. One method to identify which HARQprocesses are being used would be to add a field of k=floor(log₂(N))+1bits to an existing DCI format (referred hereafter as HARQ carriermapping) to associate the retransmission or the initial transmissionwith the proper HARQ processes.

For example, a new FDD DCI format 1 may be composed of the followingbits:

-   -   Modulation and coding scheme: 5 bits;    -   New data indicator: 1 bit;    -   Redundancy version: 2 bits;    -   Hybrid ARQ process number: 3 bits;    -   HARQ carrier mapping: floor(log₂(N))+1 bits;    -   Resource block allocation: variable, depends on the downlink        cell bandwidth.

In one example embodiment implementing the new format, a WTRU isconfigured, such as via the receipt of a configuration message, toreceive four DL component carriers (D1, D2, D3 and D4) with separatePDCCH coding received on each component carrier. The HARQ carriermapping may then be two bits. The length of this field may be cellspecific based the total number of configurable carriers for that cellor WTRU specific based on the present number of configured carriers forthat WTRU. The WTRU may be configured to determine the HARQ carriermapping, for example, using the following approach, described withrespect to component carrier D1, to decode the appropriate PDCCH:

-   (1) Search in WTRU-specific search space of component carrier D1    PDCCH candidates and decode PDCCH with corresponding DCI format    based on new DCI format length with new HARQ;-   (2) Upon positive CRC check of candidate PDCCH with WTRU-specific    cell radio network temporary identity (C-RNTI), the WTRU decodes    associated PDCCH containing the new DCI format 1.

The combination of HARQ carrier mapping field and Hybrid ARQ processnumber field maps to the appropriate 4 times 8 joint HARQ processes.

In an example of another embodiment, where the cell (C)-RNTI matches thePDCCH candidate, there is no need to change the DCI format. A WTRU withcarrier aggregation may be configured by higher layers with componentcarriers 1, 2, . . . N, with separate PDCCH coding. The WTRU may beassigned with C-RNTI_1, C-RNTI_2, . . . , C-RNTI_N. If a PDCCH candidateis received on one of the configured carriers, and matches one of theaddresses, the matching C-RNTI address combined with the Hybrid ARQprocess field value would uniquely indicate the process to be used forthe joint Hybrid ARQ of N times 8 processes.

In an example of another embodiment, the timing of the received data,similar to the embodiment described above, can also be used as animplicit additional information to determine the sub-set of the usedHARQ processes. The timing combined with the HARQ process field valuemay uniquely indicate the process to be used for the joint Hybrid ARQ.

In an example of an alternative embodiment, a WTRU may be configured totake advantage of one or more joint HARQ entities, each entity coveringa subset of all configured component carriers. In particular, a givencomponent carrier can be paired with another component carrier and use ajoint HARQ entity of 16 processes (two times 8 processes). The networkmay configure the component carrier pairing by maximizing the frequencydistance between paired component carriers. In implementation of thisexample, a WTRU with carrier aggregation may be configured withcomponent carriers D1, D2, . . . DN, and may have component carrier D1paired with D3, D2 paired with D4, . . . , D(N−2) with DN. With thisimplementation, only one additional bit may be required to define withwhich HARQ process the initial transmission or retransmission isassociated. This may be implemented by increasing the Hybrid ARQ processfield by one bit in DCI formats and by pairing semi-statically eachconfigured component carriers by higher layers. Alternatively, theaddress of the HARQ processes within the paired component carriers canalso be determined without a change in the DCI format, by making use ofthe implicit method of configuring two C-RNTIs per paired componentcarriers or alternatively by making use of the timing of the receiveddata. Therefore, the matching C-RNTI address of the paired componentcarriers combined with the Hybrid ARQ process field value would uniquelyindicate the process to be used for the joint Hybrid ARQ of 2 times 8processes. Even though the example provided herein, includes pairing ofcomponent carriers by two, it is understood that component carriers canalso be combined in groups higher than two, and the methods describedabove are still applicable.

In another embodiment, separate HARQ entities associated to theirrespective component carriers are paired together forming a joint HARQentity. An implicit association to the joint HARQ processes is based onwhether the received PDCCH is for an initial transmission or aretransmission and based on the component carrier on which the PDCCH wasreceived. For example, one rule may be that initial transmissions areassociated with a first set of 8 HARQ processes, 1-8, if received on thelowest component carrier frequency, and those received on the secondcomponent carrier are associated with a second set of 8 HARQ processes,9-16. In contrast, all retransmissions may be associated with the HARQprocess of the paired component carrier, i.e., PDCCH received on thelowest frequency component carrier are associated with HARQ processesfrom 9 to 16.

In an example implementation, a WTRU is configure to operate with Ncomponent carriers with joint PDCCH coding that includes the HARQcarrier mapping, as described in above, in each carrier specific DCIformat. This field, in combination with HARQ process in the common DCIformat, may uniquely define the joint HARQ process, N times 8 processes.

In another embodiment, a WTRU with joint PDCCH coding may be configuredto also pair component carriers together to reduce the HARQ carriermapping size, or to employ implicit rules defining which HARQ processshould be used for initial transmission and retransmission as describedabove.

The methods described herein may be used and/or implemented individuallyor in any combination. For instance, the method for identifying a subsetor a group of joint HARQ processes with a WTRU ID may be used incombination with other methods, such as an additional bit signaled inthe control channel or timing or channelization code. For instance, aconfigured WTRU ID may identify a group of 16 HARQ processes, when 32HARQ processes are jointly used, and one additional information such astiming, channelization code, etc. may further address a subset of 8 HARQprocesses within the 16 HARQ processes. Additionally, the HARQ processfield signaled in the control channel may further uniquely identify theHARQ process identity within a final 8 HARQ processes. The combinationsof the embodiment are not limited to the examples provided.

Although features and elements are described above in particularcombinations, each feature or element can be used alone without theother features and elements or in various combinations with or withoutother features and elements. The methods or flow charts provided hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable storage medium for execution by ageneral purpose computer or a processor. Examples of computer-readablestorage mediums include a read only memory (ROM), a random access memory(RAM), a register, cache memory, semiconductor memory devices, magneticmedia such as internal hard disks and removable disks, magneto-opticalmedia, and optical media such as CD-ROM disks, and digital versatiledisks (DVDs).

Suitable processors include, by way of example, a general purposeprocessor, a special purpose processor, a conventional processor, adigital signal processor (DSP), a plurality of microprocessors, one ormore microprocessors in association with a DSP core, a controller, amicrocontroller, Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs) circuits, any other type of integratedcircuit (IC), and/or a state machine.

A processor in association with software may be used to implement aradio frequency transceiver for use in a wireless transmit receive unit(WTRU), user equipment (UE), terminal, base station, radio networkcontroller (RNC), or any host computer. The WTRU may be used inconjunction with modules, implemented in hardware and/or software, suchas a camera, a video camera module, a videophone, a speakerphone, avibration device, a speaker, a microphone, a television transceiver, ahands free headset, a keyboard, a Bluetooth® module, a frequencymodulated (FM) radio unit, a liquid crystal display (LCD) display unit,an organic light-emitting diode (OLED) display unit, a digital musicplayer, a media player, a video game player module, an Internet browser,and/or any wireless local area network (WLAN) or Ultra Wide Band (UWB)module.

What is claimed is:
 1. A wireless transmit/receive unit (WTRU), the WTRUcomprising: a receiver configured to receive a first downlink controlinformation (DCI) format that does not include component carrierinformation; the receiver further configured to receive an indicationthat the WTRU is to receive a second DCI format that includes componentcarrier information; and the receiver is further configured to receive ahybrid automatic repeat request (HARQ) transmission via a componentcarrier determined from the component carrier information included inthe second DCI format.
 2. WTRU of claim 1 wherein a physical downlinkcontrol channel (PDCCH) search space is associated with the second DCIformat.
 3. The WTRU of claim 2 wherein the PDCCH search space is a WTRUspecific search space.
 4. The WTRU of claim 1 wherein the first DCIformat is a legacy format.
 5. The WTRU of claim 1 wherein the indicationis received in a configuration message.
 6. A method comprising, themethod comprising: receiving a first downlink control information (DCI)format that does not include component carrier information; receiving anindication that a wireless transmit receive unit (WTRU) is to receive asecond DCI format that includes component carrier information; andreceiving a hybrid automatic repeat request (HARQ) transmission via acomponent carrier determined from the component carrier informationincluded in the second DCI format.
 7. The method of claim 6 wherein aphysical downlink control channel (PDCCH) search space is associatedwith the second DCI format.
 8. The method of claim 7 wherein the PDCCHsearch space is a WTRU specific search space.
 9. The method of claim 6wherein the first DCI format is a legacy format.
 10. The method of claim6 wherein the indication is received in a configuration message.
 11. AeNodeB, the eNodeB comprising: a transmitter configured to transmit afirst downlink control information (DCI) format that does not includecomponent carrier information; the transmitter further configured totransmit an indication that the WTRU is to receive a second DCI formatthat includes component carrier information; and the transmitter furtherconfigured to transmit a hybrid automatic repeat request (HARQ)transmission via a component carrier determined from the componentcarrier information included in the second DCI format.
 12. The eNodeB ofclaim 11 wherein a physical downlink control channel (PDCCH) searchspace is associated with the second DCI format.
 13. The eNodeB of claim12 wherein the PDCCH search space is a WTRU specific search space. 14.The eNodeB of claim 11 wherein the first DCI format is a legacy format.15. The eNodeB of claim 11 wherein the indication is transmitted in aconfiguration message.
 16. A wireless transmit/receive unit (WTRU), theWTRU comprising: a memory, and a processor, the processor configured to:receive a first downlink control information (DCI) format that does notinclude component carrier information; receive an indication that theWTRU is to receive a second DCI format that includes component carrierinformation; and receive a hybrid automatic repeat request (HARD)transmission via a component carrier determined from the componentcarrier information included in the second DCI format.
 17. The WTRU ofclaim 16 wherein a physical downlink control channel (PDCCH) searchspace is associated with the second DCI format.
 18. The WTRU of claim 17wherein the PDCCH search space is a WTRU specific search space.
 19. TheWTRU of claim 16 wherein the first DCI format is a legacy format. 20.The WTRU of claim 16 wherein the indication is received in aconfiguration message.